-LRB- CNN -RRB- -- Joe Marshall was cruising across the San Francisco-Oakland Bay Bridge when a piece of steel and a giant cable crashed down .

He was just 50 yards away . The iReporter was just far enough away that he did n't see the debris as it fell . But he did see cars quickly move to the right lanes to avoid the mess .

The falling debris forced the closure of the bridge and snarled traffic between Oakland and San Francisco , California , as commuters look for alternate ways to get to and from the cities .

It 's also forcing structural engineers to look at key questions around the nation 's infrastructure : Has the nation done enough to address crucial bridges two years after the tragic collapse of a bridge in Minnesota that killed 13 people ?

The answer , experts say , is no .

The pieces that fell this week raise even more troubling issues because repairs had just been made in September to the same section of the 73-year-old bridge , which spans the San Francisco Bay and carries an average of 280,000 vehicles daily .

Over Labor Day weekend , crews worked to repair a damaged steel beam .

`` The bridge has been inspected , and it is now safer than when we closed it , '' Randell Iwasaki , the director of the California Department of Transportation , said at the time .

Abolhassan Astaneh-Asl , a structural engineering professor at the University of California , Berkeley , says he 's concerned that authorities took a `` Band-Aid '' approach in September . `` It failed , '' he said .

He 's worried about what he calls `` fracture-critical '' bridges : roughly 460 bridges across the country that are in dire need of repairs .

`` Following the Minnesota bridge collapse , there was a lot of discussion because of emotions , '' he said . `` I did n't really see a sustained effort that says , ` We are going to replace these fracture-critical bridges . ' ''

Federal regulators said support plates that were about half as thick as they should have been were the likely cause of the August 1 , 2007 , bridge collapse in Minnesota that killed 13 people and injured 145 .

The gusset plates -- metal plates that are meant to strengthen joists -- are believed to have failed on the I-35W bridge over the Mississippi River in Minneapolis , according to the National Transportation Safety Board .

A new bridge has since opened in Minnesota , what the American Association of State Highway and Transportation Officials hailed as one of the nation 's Top 10 transportation feats this year .

`` It is critical that our transportation systems receive the funding necessary to keep America moving . But even more important is that our state and local governments use that money to deliver projects that quickly meet the needs of our communities , '' John Horsley , the group 's executive director , said in a recent report .

But engineers say that 's the problem : Repairs are n't happening quick enough . If a tragedy like the Minnesota collapse does n't get people 's attention , they wonder , what will ?

`` I have seen some lip service , but I have not seen a lot of momentum and action , '' said William Ibbs , a professor of civil engineering at UC-Berkeley .

`` Part of that is due to the economic recession . When California has a budget deficit of $ 25 billion , they do n't worry about bridges . They worry about closing the budget gap . ''

Fari Barzegar , a civil engineering consultant based out of Oakland , says the Minnesota collapse put critical bridge problems front and center before the American public .

`` In the engineering community , we knew these things many years ago , and there were requests for money , which was n't coming , '' Barzegar said .

But he says funding has n't kept up post-Minnesota .

According to a 2009 American Society of Civil Engineers report , more than 26 percent of the nation 's bridges are either structurally deficient or functionally obsolete . The American Association of State Highway and Transportation Officials estimated in 2008 that it would cost roughly $ 140 billion to repair every deficient bridge in the country .

Bridges are typically inspected every two years .

`` If we do n't start making substantial progress in five years , we will have more collapses , '' Ibbs said .

The Bay Bridge opened in 1936 and spans 8.4 miles . It was the largest and most expensive bridge -- $ 77 million -- of its time .

The bridge is best known to most Americans from the 1989 Loma Prieta earthquake . A 50-foot section of the bridge collapsed during the quake , killing one person and prompting efforts to make it quake-tolerant .

Part of the bridge , the West Span , is a suspension bridge .

The other portion of the bridge , known as the East Span , is a truss-cantilever design .

This week 's falling debris happened on the East Span , which is in the process of being replaced .

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Falling debris on Bay Bridge raises questions about repairs after Minnesota collapse

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Bridge remains shut , snarling traffic across San Francisco Bay area

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`` I have seen some lip service , but I have not seen a lot of momentum , '' expert says